This invention relates in general to microcavity structures and in particular to microcavity structures with sharp asymmetric lineshapes.
Optical microcavity structures are of great current interests for device applications. These structures can exhibit high quality factors, and small modal volumes approaching             (              λ                  2          ⁢          n                    )        3    .
An intriguing potential application for such cavity structures is their use in optical modulation and switching. See for example P. R. Villeneuve, D. S. Abrams, S. Fan, and J. D. Joannopoulos, Opt. Lett. 21, 2017 (1996), and J. D. Joannopoulos, P. R. Villeneuve, D. S. Abrams and S. Fan, xe2x80x9cTunable microcavity and methods of using nonlinear materials in a photonic crystal,xe2x80x9d U.S. Pat. No. 6,058,127, issued May 2, 2000. The on/off switching functionality, for example, can be realized by shifting the center frequency of resonances either towards or away from the signal frequency. To achieve a large on/off contrast ratio, however, the required frequency shift tends to be much larger than the width of a single resonance to achieve switching or modulation of optical signals and other applications.
This invention is based on the observation that, by locating a resonator system adjacent to a waveguide and by employing at least two elements associated with the waveguide to cause partial reflection of electromagnetic radiation in the waveguide, a smaller frequency shift may cause a large change in the transmission and reflection of electromagnetic radiation in the waveguide.
The above-described phenomenon may be used in a number of applications, including switching or modulation of electromagnetic radiation transmission through a waveguide. Thus, switching or modulation may be accomplished by shifting the resonance frequency of the resonator system to thereby switch or modulate the transmission or reflection of electromagnetic radiation through the waveguide.
The above-described device may also be used for detecting substances. Thus, if the resonator system is placed in or in the vicinity of a certain substance, the substance may affect the resonance frequency of the resonator system. Therefore, by detecting electromagnetic radiation that is transmitted or reflected in the waveguide, an indication or measurement of the substance can be obtained.